Breeding Habits Of Black-winged Stilt In Shankou Mangrove Nature Reserve,Guangxi

The Black-winged Stilt(Himantopus himantopus)is a widespread species belonging to the Charadriiformes,Recurvirostridae,Himantopus.It is mainly breeding in northern China.But in recent 20 years,it has been found that the trend of its breeding sites to expand to the south is more obvious.At present,it has formed a stable breeding population in the coastal area of Guangxi.To explore the fitness of this new colonized population to new breeding sites,the reproductive biology of black-winged Stilt was studied at Shankou Mangrove National Nature Reserve in Guangxi from March to June 2022.The reproductive behavior,nest site selection,clutch size and hatching rhythm were studied by the methods of systematic search and focus animal sampling,and the equipments like automatic temperature recorder and so on.The results are as follows:(1)A total of 40 breeding nests of Black-winged Stilt were found,and 38 nests with 136 eggs were recorded,of which 18 were successfully hatched,with a success rate of 47.4%.(2)The courtship behavior of Black-winged Stilt appeared in March,peaked in April and basically disappeared at the end of May,taking about 7 d from courtship to pairing.Mating behavior mostly occurs at 8:00-11:00 and15:00-18:00,often in open and shallow water.Male and female collectively participate in nesting.Female started laying eggs after nesting and laid 1 egg per day for 1-4 d.Both male and female participated in hatching the eggs,and cooperative reproduction was also recorded.(3)The nests of Black-winged Stilt were mostly built on water or exposed dry beach,with outer diameter 18.806 ± 3.728 cm,inner diameter 9.759 ± 1.365 cm,and nest height 3.006 ± 1.561 cm.Principal component analysis shows that nest site selection tends to be in habitats with certain herbaceous cover and height,concealment,food availability and less disturbance.And the vegetation factors being the most important factors affecting their nest site selection.Less disturbance,high concealment and abundant food resources are important conditions for their reproductive success.(4)The eggs of the Black-winged Stilt are yellow-green or cyan piriform eggs,with black-brown spots on the surface.The average egg weight is 20.93 ±0.25 g,the average egg length and width diameter is 42.394 ± 0.238 mm and30.415 ± 0.424 mm.The clutch size is 1 to 4,with an average of 3.72 ± 0.06.Clutch size was significantly correlated with egg parameters,nest parameters,and breeding success(P <0.05).(5)The incubation period of the Black-winged Stilt was 16-24 d,average19.440 ± 0.390 d.The average daily egg weight was extremely significant negative correlation with the days of incubation(r=-0.622,P <0.01),average daily weight loss of 0.168 g.It was extremely significant positive correlation of the average temperature in nest and ambient temperature(r=0.846,P <0.01).The incabation steategy that the adults taken was higher leaving nest frequency and shorter recess time.The average daily recess was 36.020 ± 2.190 times per day,and 88.000% were concentrated at 3-20 min with an average duration of14.300 ± 0.690 min.The average daily activity time was 1133.170 ± 46.490 min,which was extremely significant positive correlation with the highest ambient temperature(r=0.458,P <0.01).There was no significant difference between breeding success and failed nests in incubation rhythm.We based on the above studies,summarized the breeding strategy and analysed of reproductive strategies of newly colonized population of Black-winged Stilt in the coastal area of Guangxi.The results show that the nesting mode was highly flexible,and the latitude difference of the nest site selection features is small.The resource allocation strategy was conservative between egg size and clutch size.The incabation steategy was higher leaving nest frequency and shorter recess time.It further explains the good fitness of the widespread species to the ecological environment,and make suggestions on resource protection and utilization.